Frost Dates for 56701 — Thief River Falls, Minnesota

Half of springs at Thief Rvr Falls 2, MN see their last 32°F night by May 14; only one in ten is past it by May 2, and one in ten still has one after May 29. Planting tender crops after May 21 leaves a 30% risk of a frost on them, after May 24 20%, and after May 29 10%. The 15 days between the even-odds date and the one-in-ten date is wider than at 64% of the 142 Minnesota stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 28 in half of years, as early as September 14 one year in ten, and holds off past October 11 one year in ten. A hard freeze of 28°F follows 10 days later, around October 8; in spring the one-in-ten date for 28°F is May 20, 9 days before the 32°F one. The freeze-free season lasts 135 days in a typical year, shorter than at 87% of the 142 Minnesota stations; it reaches 155 days one year in ten and falls short of 114 one year in ten. On average 182 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 10 days longer, to about May 24, and return around September 18. Severe cold of 16°F or below comes every winter, usually between November 5 and April 5.

July is the warmest month at Thief Rvr Falls 2, MN, averaging 80°F by day and 57°F at night; January is the coldest at 14°F and -3°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month.

Warmth for growing adds up to 2,107 growing degree days a year (base 50°F), fewer than at 74% of the 142 Minnesota stations. 33% of them (692) have built up by the end of June, and July adds the most, 564.

The nearest other station, Red Lake Falls, MN, 17 miles south of Thief River Falls, has a last frost 5 days earlier (May 9), a first frost 2 days later (September 30), a season 7 days longer.

The first measurable snow (0.1 inch or more) in Thief River Falls usually arrives around October 28, and the last of the season around April 16. Those are the middle dates across the winters of 1991–2020 at Agassiz Refuge, MN, 15.5 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 28 days after the last snow.

ZIP 56701 is 1 mile from Thief Rvr Falls 2, MN, which stands at 1,128 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 56701 in zone 4a, the band where the coldest night of the year averaged -30 to -25°F (-34.4 to -31.7°C) over 1991–2020; a zone describes winter lows, not frost dates.